The present invention relates to an apparatus and method for monitoring brake operation on a commercial vehicle. Commercial vehicles, such as tractor-trailers and buses, are generally equipped with an anti-lock braking or stability control system. These systems control vehicle braking in the event of wheel slip or instability of the vehicle by monitoring a variety of sensors on the vehicle. Some vehicles are equipped with brake wear sensing devices that indicate the wear of each brake lining. A warning is typically given to the operator when the wear exceeds a predetermined threshold. However, the brake wear sensors do not measure brake drag, which can occur when the brake shoe or brake pads are not completely released at the completion of a service brake application. The brake wear sensors do not measure an underperforming brake, which can occur when the brake at a particular wheel end does not apply as quickly or as fully as the other wheel end brakes on the vehicle. Information from the wear devices and sensors associated with the stability control system are typically evaluated instantaneously during vehicle operation, which does not indicate any long-term trends in the brake operation. These brake wear systems are typically separate from the anti-lock braking or stability control systems so that any information learned from the brake wear system is not used to improve braking performance.